1. Field of the Invention
The present invention relates generally to exhaust gas purification systems for engineering machines. More particularly, the invention concerns an exhaust gas purification system for engineering machines of a traveling type, such as hydraulic excavators, each of the machines including a regenerating device to burn off a deposit of particulate matter from a filter disposed for trapping the particulate matter contained in gas emissions, and regenerate the filter.
2. Description of the Related Art
Conventional exhaust gas purification systems for purifying diesel engine gas emissions include the systems described in JP,A 2005-120895 and JP-3073380, for example. The exhaust gas purification system described in JP,A 2005-120895 has a filter, called a diesel particulate filter (DPF), in the engine exhaust line of a truck or any other transport vehicle to trap the particulate matter (PM) contained in gas emissions and reduce the amount of PM released to the outside. In order to prevent the clogging of the PM filter, the purification system in JP,A 2005-120895 is also adapted to conduct automatic regeneration control and manual regeneration control. Automatic regeneration control detects the differential pressure across the filter, then discriminates the estimated amount of PM deposited thereupon, and if this estimated amount of PM exceeds a first threshold level, increases the temperature of the gas emissions automatically to burn off the PM from the filter. Manual regeneration control, which, if the estimated amount of PM exceeds a second threshold level greater than the first threshold level, prompts an operator to start manual regeneration control under a stopped state of the vehicle by activating a warning lamp, and when the operator turns on a manual regenerating switch, increases the temperature of the gas emissions to burn off the PM deposited on the filter. The temperature of the gas emissions is increased by the oxidation of unburnt hydrocarbons (HC) due to additional fuel injection during the expansion stroke of the engine after main injection.
The exhaust gas purification system described in JP-3073380 regenerates a filter in a hydraulic engineering machine by burning off deposits from the filter after engine output has been enhanced by loading the engine in a hydraulic-like manner for an increased gas emissions temperature. The purification system in JP-3073380 the exhaust resistance of the engine due to the use of the filter and start the regeneration of the filter automatically if the exhaust resistance exceeds a permissible level.